Refrigeration



April 9,1940. GE] 2,196,778

REFRIGERATION Filed Sept. 5, 1939 1 33 E 37 29 C 27 I E v E f) Q5 24 2 E--s 22 M 6 21 E 19 3 I: 18 L 20 l: E 7 17 12 6 V 5 E 15 j I I 3maentorPatented Apr. 9, 1940 UNITED STATE 7 REFRIGERATION Parker Dodge, ChevyChase, MIL, assignor to Johnson Service Company, Milwaukee, Wis., acorporation of Wisconsin Application September 5, 1939, sci-in No.293,475

6 Claims.

This invention relates to refrigeration, and particularly to means forcontrolling the supply of refrigerant to an evaporator in response tothe temperature of a space cooled by such evaporator.

Prior to the present invention, it has been proposed to cause a smallexpansion valve of the superheat control type to pilot the action of alarger valve (known as a booster valve) which controlled the fiow ofrefrigerant to the evaporator. In this way, a small and inexpensiveexpansion valve, which, because of its small internal friction, can bemade very sensitive, can accurately control supply of refrigerant to alarge evaporator.

' In the operation of certain cooling plants, notably air conditioners,it is desirable to reduce the supply of refrigerant to the evaporator inresponse to falling temperature and thus reduce the total refrigeratingeflect.

The present invention provides a method of controlling a booster valvein such a way that when temperature of the cooled space is at or above achosen value, apilot valve of the superheat control type exercisessolecontrol. As temperature of the cooled space falls below. such value,a space. thermostat increasingly modifies and then suppiants the controlexercised by the pilot valve, causing the booster valve to close moreand more with falling temperature.

The scheme is safe because the space thermostat can reduce but neverincrease the rate' of feed of liquid refrigerant beyond theilimitsimposed by the superheat pilot valve. It is inexpensive and accuratebecause the mechanism controlled by the space thermostat is small andhas slight internal friction.

A simple embodiment of the invention is illustrated in the accompanyingdrawing in which the single figure is a view largely in section as tothe 40 control means and illustrating the refrigerating circuit with thecompressor and condenser indicated in diagram.

a The means for drawing refrigerant from the evaporator andforllquefying it would be, conventional, and may assume any form known inthe refrigerating art. For example, the invention can be used with anabsorption system.

In the drawing, the pipe I is the suction line leading to the compressordiagrammatically indicated at M. The compressor M delivers hotcompressed vapor to a condenser diagrammatically indicated at. C inwhich it is cooled and thus caused to assume the liquid phase. From thecondenser C, the liquid refrigerant is fed through connection 2 to thereceiver 3.

The ,valve 4 is an ordinary suction limiting valve. The use of this isoptional. When used, it prevents, or at least limits, the reduction ofevaporator pressure and consequently the reduction of evaporatortemperature, which would otherwise occur if the compressor shouldcontinue to operate at its normal volumetric rate while the supply of.refrigerant to the evaporator is restricted. The use of suction limitingvalves iswell known, and one is here illustrated w to indicate thepossibility of its inclusion, if 'de-" sired.

From the receiver 3, the liquid line 5 leads to the booster valvegenerally indicated by the numeral 6 applied to its body. The dischargeside 5 of the valve is connected at l to the header 8 of an'evaporator,some ofwhose tubes are indicated at 9. The evaporator suction connectionii leads from the upper end of header 8 to suction line I, the limitingvalve 4 being interposed, Y0

' if desired. T

The booster valve 6 is preferably of the balanced typeso as to beindifferent to pressure of flowing liquid reacting on the valve, and'isshown as comprising two poppet valve heads l2 and i3 on a common stemI4, and coacting with spaced seats in a shell l5, through which seatsflow occurs in opposed directions from the inlet to the outlet of thevalve. The stem II is urged upward by a light compression spring It sothat head I! ls held in engagement with a flexible diaphragm It.

The diaphragm is clamped at its periphery between the body 6 of thebooster valve and a bonnet l9 bolted thereto. It is subject on its lowerface to the pressure of liquid refrigerant arriving through liquid line5 (head pressure) and is loaded in the opposite (valve closing)direction by coil compression spring 20.. The stress on spring 20 isadjusted by a serewj i, 4o sealed by cap 22. The diaphragmis also loadedby fluid pressure communicated through pipe 23, as will be explained.

A by-pass connection 26 leads from the receiver 3, preferably but notnecessarily abov the liq- -uid level therein, to a pressure motoroperated throttling valve'25 and a restricted fiow orifice V fitting 26connected in parallel between connection 24 and a connection 2'l, whichleads to the superheat control expansion valve 28, and to 50 which thepipe 23 is also connected.

The fitting 26 is preferably arranged according to known practice toreceive interchangeable orifice plates of different capacities. Thevalve 25 is operatedby'a bellows motor 29 connected 5 by capillary tube3| with bulb 32 which contains a liquid adapted to develop a suitablerising pressure in response to rising temperature. pressure reacts uponmotor 29 to close the valve 25 in opposition to a spring 33 which biasesthe valve in its opening direction.

The parts are so arranged that valve 25 closes when bulb 32 (which issubject to conditions in the cooled space) is at or above the chosentemperature and opens gradually as bulb temperature falls below thatvalue.

The superheat control expansion valve 28 is preferably of the type inwhich a flow controlling valve responds to a valve closing forceproportional to evaporator pressure, and a valve opening forceproportional to temperature of refrigerant leaving the evaporator. It isso loaded as to reach equilibrium under conditions such that refrigerantleaving the evaporator is slightly superheated. Such valves are incommon use and are manufactured in many commercial forms.

One form, which is shown and described in the patent to Newton No.2,120,764, June 14, 1938, is illustrated in detail in the drawing, andrequires no description beyond the general statement of its functionabove given. Its thermostatic bulb 34 is applied to suction connection Il, and affects the valve 28 through capillary tube 35. The valve 28discharges through connection 31 to any point at evaporator pressure,conveniently the top of header 8.

The flow capacity of fitting 26, the stress'on spring 20, and theoperating characteristics of valve 28 are so coordinated that when valve25 is closed, i. e., when temperature at bulb 32 is at or'above thechosen value, valve 28 pilots the booster 6 to give the desired slightsuperheat at connection H. The effect is usually to operate evaporator8'9 nearly flooded, but the invention is not limited to flooded actionand does not exclude other known operative characteristics for theevaporator attainable with superheat control valves.

As temperature at bulb 32 starts to fall below the chosen value, valve25 starts to open. For any asumed position of valve 28, pressure abovediaphragm l8 will rise as valve 25 opens, thus closing the booster valveslightly. Within a limited range, valves 25 and 28 control conjointlyfor opening of valve 25 increases the pressure on diaphragm I8 so thatthe booster valve closes somewhat. This reduces evaporator pressure andmay increase the temperature at bulb 34because of the reduction of totalrefrigeration. In any event, valve 28 tends to open and restore balance,seeking, as it does, to limit superheat. If valve'25 opens far enough,valve 28 opens wide, and from then on valve 25, if it open further,alone controls the booster valve.

If theline 24 leads from above the liquid level in the receiver asshown, the secondary path via 24, 2B (25) 21, 28, 31, passes onlyrefrigerant vapor. This is preferred because the refrigerating effect ofthe small volume of vapor is negligible whereas the use of liquidrefrigerant would involve a larger refrigerative effect and require theuse of much better insulation of the secondary path to ensure stableaction.

While I prefer to use the superheat control type of expansion valve topilot the booster valve, as shown, other types of automatic expansionvalve are known and may be substituted. In such case,

the space thermostat modifies their action inan analogous way. a

While a choke by-pass around valve 25 15 bevchamber, the pressure inwhich serves to adjust the booster valve; a thermostatic valveresponsive to a temperature influenced. by said evaporator and servingabove a chosen temperature to establish a minimum flow rate from thereceiver to I said chamber and as temperature falls below said value toenlarge said flow rate; and an automatic expansion valve connectedbetween said chamber and a point in the circuit at evaporator pressure.

2. The combination of a refrigerating circuit including an evaporatorand a receiver; a booster expansion valve controlling flow ofrefrigerant from receiver to evaporator and including a motor chamber,the pressure in which serves to adjust the booster valve; a thermostaticvalve interposed in a connection between the receiver and said motorchamber, responsive to a temperature influenced by said evaporator andserving above a chosen temperature to establish a minimum flow rate fromthe receiver to said chamber and as temperature falls below said valueto enlarge said flow rate; and an expansion valve responsive to thesuperheat at the evaporator outlet connected between said chamber and apoint in the circuit at evaporator pressure.

3. The combination defined in claim 2 in which the receiver is onlypartially liquid filled and the connection from the receiver to thechamber leads from a point above the liquid level in the receiver.

4. The combination of a refrigerating circuit containing a volatilerefrigerant and including an evaporator, means for withdrawingevaporated refrigerant from the evaporator and for liquefying the sameat a pressure higher than that in the evaporator, and a valvecontrolling the delivery of liquid refrigerant from said liquefyingmeans to the evaporator; a pressure motor connected to actuate saidvalve and comprising a movable abutment subject in a valve openingdirection to the pressure in said liquefying means, and in a valveclosing direction to pressure in a chamber; means for biasing said valvein a closing direction; means forming a by-pass from said liquefyingmeans to said'chamber and thence to a point in the circuit at evaporatorpressure; an expansion valve responsive to the superheat at theevaporator outlet controlling said by-pass' between said chamber and thepoint at suction pressure; regulating valve means interposed between theliquefying means and said chamber and operable to establish a minimumfiow rate and to enlarge the flow rate above such minimum; andthermostatic means subject to a temperature affected by said evaporatorand connected to control said regulating valve means, the parts being soarranged that above a definite temperature the minimum fiow rate'isefiective, and as temperapansion valve controlling flow from condensersaid controls being responsive to a combined effect of evaporatorpressure and temperature of refrigerant withdrawn from the evaporatorandthe other responsive to the efiect of temperature in a space cooledby said evaporator.

PARKER DODGE.

